The 12-month randomised, double-blind, placebo-controlled trial, compared several herbal regimens and menopausal hormone therapy (oestrogen with or without progesterone) to placebo in women ages 45 to 55. The study was conducted by Katherine M. Newton, Ph.D., of the Group Health Center for Health Studies in Seattle.

Three-hundred and fifty-one women, ages 45 to 55, took part in the study. Each participant was experiencing at least two hot flashes and/or night sweats daily at the start of the study. The women were approaching menopause, having missed at least one menstrual cycle in the preceding twelve months, or were postmenopausal, having had no menstrual cycle in at least twelve months. Researchers included women who were perimenopausal or in the menopause transition.

Initially, the women were randomly assigned to receive one of five therapies: Black cohosh, a multibotanical supplement, a multibotanical supplement plus diet counselling to increase consumption of foods containing soy, a menopausal hormone therapy consisting of oestrogen with or without a progestin, and a placebo group. Participants met with clinic staff at three, six, and twelve months after the beginning of the study and also received monthly telephone calls from study nurses.

Newton and colleagues found no significant difference between the number of daily hot flashes and/or night sweats in any of the herbal supplement groups when compared to the placebo group. At the end of one year, the average difference was less than 0.6 symptom per day. However, the average difference at one year in symptoms between the menopausal hormone therapy and placebo group was significant - 4.06 fewer symptoms per day among women receiving hormones.